1. Field of the Invention
The present invention relates to a multi-point mobile communications system.
2. Description of the Related Art
As the network environment has been diversified, a variety of visual communications equipment with a variety of transmission speeds and protocols corresponding to a variety of networks have been put to practical use. In particular, recently the need for visual communications by a mobile object has been increasing and it is required that visual communications using a radio network are implemented with a simple configuration and a low cost. The coverage of visual communications via a radio network has been expanded and the wide collection of pictures has become available. In the meantime, a center using pictures has a request for simultaneously receiving pictures from many types of mobile communications equipment. One application of such a visual communications system using a radio network is fire fighting. A fire-fighting communications system is configured to connect the front and back of a fire site, a fire station, etc., with one another, to receive information (image/voice) from an arbitrary point and to conduct prompt and efficient fire fighting.
FIG. 1 shows the concept of the application form of a visual communications system using a radio network.
A visual communications system using a radio network can also be applied to a construction communications system for connecting a construction site, a construction office, headquarters, etc., with one another and to receive information from an arbitrary point, in addition to the fire-fighting communications system. In this case, information can be transmitted from the construction site to the construction office and vice versa, and thereby the construction site can be effectively supervised by the construction office.
In conventional visual transmission over a radio network, one-directional transmission from mobile equipment to a fixed station was common and one-to-one communications were conducted. Multi-point communications in visual transmission using a fixed network, such as ISDN (Integrated Services Digital Network), etc., generally requires an expensive dedicated device for connecting and controlling a plurality of points, called a multi-point conference device.
Mobile communications use a radio network. A radio network has a transmission band narrower than a fixed network. Under such an environment, information (image/voice) must be transmitted among a plurality of points. Terminals for mobile communications must be able to be used in a variety of places and must be inexpensive. An entire system must also be inexpensive. In these situations, an expensive multi-point visual communications system using a radio network must be configured without using a dedicated device, such as a multi-point conference device.
An object of the present invention is to provide a multi-point mobile communications system for communicating among a plurality of terminals used in peer-to-peer.
The multi-point communications system of the present invention comprises at least two terminal units for acquiring information, transmitting over a radio network and temporarily stopping transmitting/receiving information while holding a communications session, if required, and a received information interpreting unit which accomodates more channels than the number of terminal units but fewer than the channels to be accomodated. The multi-point communications system further comprises a main terminal unit for temporarily stopping transmitting/receiving information while allowing the terminal unit currently connected to hold a communication session and connecting the terminal unit which requests a new connection to the network, if there is a new connection request from one terminal not yet connected to the network of the at least two terminal units while the other terminal unit of the at least two terminal units is connected to the network.
The multi-point communications method of the present invention implements multi-point communications between at least two terminal units for acquiring information, transmitting over a radio network and temporarily stopping transmitting/receiving information while holding a communications session, if required via a master terminal unit with a received information interpreting unit which accomodates more channels than the number of terminal units but fewer than the channels to be accomodated, and comprises the steps of temporarily stopping transmitting/receiving information while allowing the terminal unit currently connected to hold a communications session and connecting the terminal unit which requests a new connection to the network, if there is a new connection request from one terminal not yet connected to the network of the at least two terminal units while the other terminal unit of the at least two terminal units is connected to the network.
According to the present invention, multi-point communications can be conducted using a simple and inexpensive device. In particular, although a conventional TV conference system uses a network connected by wired lines, the present invention can use a network with a band narrower than a wired network, such as a radio network. Although in the conventional TV conference system, a master server (master terminal) was provided with the same number of codecs as channels, in the present invention, multi-point communications can be conducted with fewer information reception interpreting devices than the number of channels, for example, with codecs, or a master terminal provided with only one information reception interpreting device. Therefore, there is no need to provide many expensive information reception interpreting devices, and a system with an inexpensive and simple configuration is available. By using a radio network, the mobility of a terminal can be improved and thereby a variety of information can be acquired from a variety of sites.